Who makes the ideal carbonfiber Porsche parts, especially for a 993?

What kind of parts? A lot of carbon fiber parts will be trim accessories (such as door sills, gear shift knobs, etc). These parts are made by all the companies you'd anticipate to offer such items, and the quality you can anticipate from these would be the same as you would for any other items they might offer (ie, Momo is more of a quality name for a gear shift knob than the local auto parts store in home brand).

Race shells? Sparco and Recaro would be the main companies in this space. Carbon fiber will definitely be the lightest here, though wear and tear lead many racers to look at other kinds of seats (tough to justify a few thousand for a seat each couple years).

Bodywork? A few companies offer parts, though they’re often hard to evaluate. Most of the companies that do bodywork fabrication for Porsche seem to use fiberglass as their lightweight item of choice, and these are the parts I see most often on racecars. Though there are some carbon fiber parts out there, which will be marginally lighter than the fiberglass (for a lot more money). The ideal bet here’s to find a Porsche bodyshop that’s an expert with Porsches (ask around with PCA members in your area), and then talk with them about the items you want and which they have seen that have been both well made and have had the ideal fit and finish when done.